tick tick tick 150 cc gy6
 

howdy dawgs!

So over the winter I adjusted the valve clearance and the scooter is running fantastic. Signifigant improvement in the MPG too!

but I'm noticing a tick, it's getting somewhat annoying I suspect that perhaps my valves are now too loose?

Thoughts?

Probably. The best way to double check yourself after doing a valve adjustment is to rotate the engine around to the timing location again and check the clearances. Sometimes you're not at precisely the right spot and the cam was out of location enough to affect the adjustment. A few times I did that and the clearance was slightly wrong and required a re-do.

KZ is right, should spin the engine a couple of revolutions, and recheck gaps...then button things up.

That being said, better a bit loose than a bit tight....."ticking valves are happy valves"

Guess you have proven that saying to be true....cuz you said "it's running fantastic...significant improvement in mpg too"

It may be yours are a bit too loose.....but if you can't hear any ticking, they are definitely too tight.

I had not heard that before lol! good to know. If my Valves are happy then I'm happy!
I'll check the clearance again, if it's in spec I wont sweat it!

Thanks for tip KZ, makes total sense to rotate the engine and double check. seems so obvious not sure why I didn't think of it! makes me feel silly!

You didn't say what you set the gaps to. The mm values in the manuals, and the inch stamping on so many feeler gauges, get some people mixed up. The set of feeler gauges I have are marked in both units of measurement.


Most will agree that a good setting for a 150cc engine is, intake .004 inches, and exhaust .005 inches

Interesting point! I 99.9% sure I set them to .004in and .005in but now that you mention it I'm questioning that lol, I had the intention of setting them to .004in and .005in as thats what I read in forums and is stated in all the you tube videos :tup: would the scooter even run if I had gone an order of magnitude too loose (.05 in vs .005)? do my feeler gauges go that big? :thanks:

So yeah, valves we're on the loose side, not way outta whack but loose just the same, I cold get the .006 blade into the exhaust side pretty easy and move it freely, I tightened things up a little and it still ticks but not like it did...

Thanks Guys!

Ticking is *not* good for the valve. RUN AWAY from anyone that says this. Let me explain why.

As the cam shaft rotates and the cam lobe approaches the valve, ideally it starts picking up the lobe as soon as the lobe starts changing shape. The lobes are profiled so that the initial rate of lift is slow, then it accelerates to fully open, slows, starts closing, accelerates towards closed, then slows before completely closing.

You hear the ticking sound because the valves are too loose. If the adjustment is too loose, you end up skipping the gradual speed change at the beginning, and end, of the valve cycle. There is now no initial slow lift, and the cam lobe basically slams into the valve (faster than intentioned). Additionally, there is no deceleration at the end of the cycle, and the valve slams shut against the cylinder head. This puts a ton of stress on the valves, especially at high rpms. It is not good for the longevity of the engine, and could result in catastrophic failure if the valve stems bend (due to getting whacked at the start of the cycle) and seize the valve, or damage of the valve due to slamming back into the cylinder head.

Conversely, if the valve adjustment is too tight, the valves don't come to a complete close, and you lose compression (and therefore, power).

Well, now you have opposing opinions. I like ticking....some like things a bit tight

.004 and .005 are the right settings, and as the engine warms up to normal operating temperature these gaps will decrease. They will also very likely decrease over the next 2000 miles of operation, depends on how new your scooter is. I've found that they will hold an adjustment longer, once you get past the first 2500 miles or so.

At a leisurely 6000 rpm cruising speed, your valves are opening and closing 50 times a second. At idle, they're working 13 to 15 times a second. How you can achieve a gradual opening, or a gentle closing of the valves, at those speeds.....I don't know.

Little or no gap doesn't leave much room for oil to get between the moving parts. Maybe an extra .001" will provide a little better lubrication.

As a side note....my BMW's are air cooled, 2 cylinder, overhead cam engines, with 4 valve heads.....Gap spec for these engines...intake .006", exhaust .012". Valves make noise...tick, tick, tick. Thing is, they will do this for 100,000 miles or more. Some make 200,000 miles before a rebuild is in order.

Interesting opposing views.

When a vehicle manufacturer states a specification such as valve adjustment, that spec IMO should be followed. Even though many of us have lots of experience, we still do not possess the designers knowledge of how he wanted that engine to perform. He had considerations of wear, function, life expectancy, and yes noise that might irritate the customer in his original design. To him it is a balancing act trying to achieve all the stated manufacturer goals.

I have yet to see any manufacturer state valve adjustments to be performed on warm or hot engines. Years ago, we adjusted valves while the engine was operating, but still cold or cool. Thus the tolerance for heat expansion was considered in the spec.

When the manufacturers went to hydraulic lifters, this was done to not only control noise but to increase engine life and reduce wear. And of course maintenance.

As rks points out in his example, each valve would be opening at 100 times per second @ 6k and if the tolerances are off either way damage can be the result. As shadowfire points out too loose and the valves seat harder via the spring pullback, this can damage valves & seats. The damage may not be noticeable until it gets really bad. Also you lose a little opening time, thus reduces A/F charge into the cylinder.

If too tight then the valve may remain open enough to burn or stretch resulting in engine damage.

I set both of mine at .005. Is that ok?

It's fine. Years ago when I first started in a machine shop someone plucked out one of my hairs and put in a micrometer. It was about .005 inch. You might damage a cam or valve at .015 or .020 inch but being within one or two thousandths on the loose side isn't going to kill anything. Not with valves opening and closing 50 times per second.

Thanks!

Just did my first valve adjustment
 

I REVISE WHAT I HAVE SAID BELOW

Have 45 miles on my BMS Prestige 150. I was advised I should change the oil (before recommend 150 mile break in) and check/adjust valves. I noticed a TICK after I adjusted it like OP, and think I know why.... more below. What I did...

There is a data tag right on the bike with specs.

INTAKE 0.003-0.004
EXHAUST 0.005-0.007

Intake was 0.004 and left it alone. The exhaust was at or under 0.004. So I adjusted it to 0.006", assuming it was midway. This was before reading the internet wisdom that 0.005" was magic, even less.

Why do you become hyper aware of a sound that was already there before? The OP valves were probably ticking before to some degree. Once you work on it, seat and fairing off, ear paid full attention, you hear it. Hyper aware, I noticed a small tick when COLD.

There is a phenomenon when flying little planes out over the ocean or rough terrain. As soon as you get feet wet or over wilderness, the engine runs rough (or you think it is). It is not running rough, it is just your imagination. It is called "auto-roughness". Same with valves. There is ALWAYS some valve train noise... However I you may have made a mistake...

With that said I'll go back and check and adjust the Exhaust to 0.005". You don't want mechanical lifter valves too lose or too tight.

If you get it so tight the valve (especially the exhaust) does not seat, and you get blow-by. On the exhaust that can cause burnt valve and valve seat.

WELL I WENT BACK AND ADJUSTED EXHAUST VALVE. I THOUGHT I HAD SET IT TO 0.006. IT WAS WAY LESS. I RESET IT AND DOUBLE, TRIPLE CHECKED AND SET IT TO 0.005. NO MORE TICK TICK TICK... HUMMM.

I know that I've expressed my opinions on this subject in earlier posts, but that was over 2 years ago.

On my way home today, my scooters odometer crossed the 12,500 mile mark. My last valve adjustment was performed over 10,000 miles ago, on June 17, 2013, at 2,502 miles. I have checked them annnually, but they have been fine. Scoot still starts very quickly, has always idled the way it should, and still runs great.....and oh yes, my valves still go tickety-tick, tickety-tick.